1. Field of the Invention
The invention relates to an electric dust collecting unit and, more particularly to, the electric dust collecting unit suitable for use in a diesel engine exhausted carbon particulate removing apparatus, a factory oil mist removing apparatus or a like.
The present application claims priority of Japanese Patent Application No. Hei11-324717 filed on Nov. 15, 1999, which is hereby incorporated by reference.
2. Description of the Related Art
Since offices, restaurants, amusement places, factories, housing, and other buildings have recently been of an airtight construction, cigarette smoke, toner, welding fumes, and other harmful particulates floating in air are more likely to damage human health in a building, contaminated facilities and equipment. To guard against this, there has been widely employed an air cleaner which is placed in the office or housing, to collect cigarette smoke, particulates, and offensive odors floating in the air. One such type of air cleaner is known as a needle-discharge type air cleaner disclosed in Japanese Patent Application Laid-open No. Hei9-285739 (Japanese Patent No. 2733908), Japanese Patent Application No. Hei11-125451 (Japanese Patent No. 3092112), and others. This air cleaner roughly has such a configuration that, as shown in FIG. 8, its apparatus box body 3, having an air inlet 1 and an air outlet 2, includes a panel-shaped pre-filter 4, a box-shaped electric dust collecting unit 5, a panel-shaped deodorizing filter 6 made up of an activated carbon filter, and a ventilating fan 7, which are all mounted serially from a windward side to a leeward side therein.
In the above-mentioned configuration, when the ventilating fan 7 operates, air in a room is drawn in. If, in this case, the air in the room has been contaminated with cigarette smoke or other floating particulates, first the panel-shaped pre-filter 4 captures relatively large particulates, to permit other relatively small particulates that could not be captured by the panel-shaped pre-filter 4 to be captured and removed by the box-shaped electric dust collecting unit 5. Still remaining cigarette odor is absorbed and removed by the panel-shaped deodorizing filter 6. In this manner, cleaned air is returned to the room via the air outlet 2 by exhausting force of the ventilating fan 7. The boxed-shaped dust collecting unit 5 or a like, if contaminated with particulates or a like stuck thereto, may be taken out from the apparatus box body 3, washed, rehabilitated, and then mounted in the apparatus box body 3 again for use.
As shown in FIGS. 9 and 10, the boxed-shaped electric dust collecting unit 5 has a box-type frame 5a which includes a plurality of disk-needle-shaped needle electrodes 5b, prism-shaped deflecting electrodes 5c for supporting and fixing these disk-needle-shaped needle electrodes 5b in a protruded state, and both-ends-opened rectangular-shaped collector cells (collecting electrodes) (hereinafter may be referred to as collector cells 5d) for surrounding these disk-needle-shaped needle electrodes 5b and prism-shaped deflecting electrodes 5c in an non-contact manner which are all arrayed in a lattice and in combination in such a manner that there may be provided an air-passage gap between each of the prism-shaped deflecting electrodes 5c and its corresponding collector cell 5d. 
When, in this configuration, a DC voltage of for example 5-6 V is applied between a disk-needle-shaped needle electrode 5b and its corresponding prism-shaped deflecting electrode 5c, which are both positive in potential, and its corresponding negative-potential electrode collector cell 5d, uniform corona discharge persistently occurs in a stable manner around the sharp tip of a disk-needle-shaped needle electrode 5b, thus forming an ionized space region 5e as shown in FIG. 11. When, in this state, the ventilating fan 7 operates to permit contaminated air inhaled via the air inlet 1 (FIG. 8) to reach the ionized space region 5e of the box-shaped dust collecting unit 5, oxygen is first dissociated into positive ions, which in turn stick to particulates p of cigarette smoke or a like and charge them electrically. The charged particulates xe2x80x9cpxe2x80x9d pass through between a next prism-shaped deflecting electrode 5c and its corresponding collector cell 5d, during which they are attracted to the collector cell 5d with a negative (lower) potential if they are near that collector cell 5d. If they are far away from a electrode plate(not shown or labeled) of the collector cell 5d, on an other hand, the particulates xe2x80x9cpxe2x80x9d are near the electrode plate (not shown or labeled) of the prism-shaped deflecting electrode 5c with a positive (higher) potential, so that they get Coulomb resiliency to move toward the electrode plate (not shown or labeled) of the collector cell 5d, thus finally being attracted and captured by the collector cell 5d. 
In the above-mentioned prior art box-shaped electric dust collecting unit 5, however, as shown in FIGS. 9 and 10, the sharp tip of the disk-needle-shaped needle electrode 5b faces to an opened front face of the box-type frame 5a, therefore an operator may be injured by the needle electrodes when washing, maintaining or inspecting the boxed shaped electric dust collecting unit 5, thus holding a manufacturer responsible for handling safety.
In view of the above, it is an object of the invention to provide an electric dust collecting unit capable of safe replacement, washing, and maintenance and inspection.
According to a first aspect of the present invention, there is provided an electric dust collecting unit including:
a corona discharging portion for giving rise to corona discharge to thereby electrically charge floating particulates in an airflow; and
an electric collecting portion disposed on a leeward side of the corona discharging portion, for electrically collecting the floating particulates charged at the corona discharging portion,
wherein the corona discharging portion includes a plurality of needle electrodes in which each has a sharp needle tip and also which is arranged in such a way that the sharp needle tip thereof may be directed toward the leeward side.
In the foregoing, a preferable mode is one wherein the corona discharging portion and the electric collecting portion are disposed as separated from each other space-wise with or without an insulating material interposed therebetween.
Also, a preferable mode is one wherein the corona discharging portion includes:
the plurality of the needle electrodes which each has the sharp needle tip and also which is arranged in such the way that the sharp needle tip thereof may be directed toward the leeward side; and
a plurality of opposing electrodes which is disposed in an n-to-one opposing relationship with the needle electrodes, where the n is a two or larger natural number representing number of the needle electrodes, and also which each has both ends thereof opened for forming an airflow passage.
Also, a preferable mode is one wherein the corona discharging portion includes:
the plurality of the needle electrodes which each has the sharp needle and also which is arrayed in such the way that the sharp needle tip thereof may be directed toward the leeward side; and
a plurality of cell-shaped opposing electrodes which is disposed in a one-to-one opposing relationship with the sharp needle electrodes and also which each has both ends thereof opened for forming an airflow passage.
Also, a preferable mode is one wherein the corona discharging portion includes:
the plurality of the needle electrodes which each has the sharp needle tip and also which is disposed in such the way that the sharp needle tip thereof may be directed toward the leeward side;
one or more of supporting electrodes for supporting and fixing the plurality of the needle electrodes; and
the plurality of the cell-shaped opposing electrodes which is disposed on a leeward side of the one or more supporting electrodes in the one-to-one opposing relationship with the needle electrodes and also which has the both ends thereof opened for forming the airflow passage.
Also, a preferable mode is one wherein each the needle electrodes are supported by the supporting electrodes with at least the sharp needle tip thereof as driven into an internal cavity of the cell-shaped opposing electrodes.
Also, a preferable mode is one wherein the one or more supporting electrodes are made of a rod-shaped member or an elongated member and has thereon the plurality of the needle electrodes supported and fixed in a row with a predetermined spacing therebetween.
Also, a preferable mode is one wherein the rod-shaped member or the elongated member of the one or more supporting electrode has a plurality of mounting holes made therein in a row with a predetermined spacing therebetween, each of which has corresponding one of the needle electrodes supported and fixed, as fitted therein.
Also, a preferable mode is one wherein the electric collecting portion includes:
a collecting electrode for electrostatically attracting and collecting floating particulates charged by the needle electrodes; and
a deflecting electrode provided correspondingly to the collecting electrode, for providing the floating particulates which are charged, with deflecting force toward the collecting electrode.
Also, a preferable mode is one wherein the electric collecting portion has thereon the collecting electrode which is plate-shaped and the deflecting electrode which is plate-shaped as disposed in parallel with each other with a predetermined mounting spacing therebetween.
Also, a preferable mode is one wherein the opposing electrodes are made up of paper or synthetic resin coated with metal.
Also, a preferable mode is one wherein the opposing electrodes are made up of a stack of paper or synthetic resin and metal foil.
wherein the cell-shaped opposing electrodes are made up of paper or synthetic resin coated with metal.
Also, a preferable mode is one wherein the cell-shaped opposing electrodes are made up of a stack of paper or synthetic resin and metal foil.
Also, a preferable mode is one wherein at least one of the collecting electrode and the deflecting electrode is made up of paper or synthetic resin coated with metal.
Furthermore, a preferable mode is one wherein at least one of the collecting electrode and the deflecting electrode is made up of a stack of paper or synthetic resin and metal foil.
According to a second aspect of the present invention, there is provided an electric dust collecting unit including:
a corona discharging portion for giving rise to corona discharge to charge floating particulates in an airflow; and
an electric collecting portion disposed on a leeward side of the corona discharging portion, for electrically collecting the floating particulates charged by the corona discharging portion, wherein:
the corona discharging portion includes a plurality of needle electrodes which each has a sharp needle tip and also which is disposed in such a way that the sharp needle tip thereof may be directed toward a leeward side, a plurality of rod-shaped or elongated supporting electrodes separately disposed from each other with a predetermined spacing therebetween, for supporting and fixing the plurality of the needle electrodes, and a plurality of cell-shaped opposing electrodes which is disposed on a leeward side of the plurality of rod-shaped or elongated supporting electrodes in a one-to-one opposing relationship with the needle electrodes and also which each has both ends thereof opened for forming airflow passage;
the electric collecting portion includes a plate-shaped collecting electrode for electrostatically attracting and collecting the floating particulates charged by the needle electrodes and a plate-shaped deflecting electrode provided correspondingly to the plate-shaped collecting electrode, for giving the floating particulates which are charged, deflecting force toward the plate-shaped collecting electrode, in such a configuration that the plate-shaped collecting electrode and the plate-shaped deflecting electrode are alternately disposed in parallel with each other with a predetermined spacing therebetween; and
a mounting spacing between the plate-shaped collecting electrode and the plate-shaped deflecting electrode is set shorter than a mounting spacing between the plurality of rod-shaped or elongated supporting electrodes.
With the above configuration, the needle tip of each needle electrode is disposed and provided as directed toward the leeward side, in other words, with its back directed toward the front face opening in the electric dust collecting unit, so that the worker or the operator can be prevented from being injured his fingers or body by the needle tip, thus resulting in safe replacement, washing, and maintenance and inspection of the electric dust collecting unit. Therefore, the electric dust collecting unit of this embodiment is applicable not only to an office-use air cleaner but also to a home-use air cleaner.
In addition, since the prior art prism-shaped deflecting electrode is not used, airflow passage is not pressured, to thereby reduce pressure loss remarkably, thus contributing to miniaturization of the electric dust collecting unit, hence an air cleaner.